9/23/2011 9:55 AM PDT BY TMZ STAFF

"Biggest Loser" competitor Sam Poueu -- who was listed in critical condition after falling several stories from a fire escape this month -- is making some serious progress in his recovery and has been upgraded to stable, TMZ has learned.

We're told doctors are still wary because Sam's status could change at any moment -- but overall, everyone's excited by his progress.

As we previously reported, Sam was celebrating a friend's birthday when he accidentally locked himself on the roof -- and fell several stories while trying to climb down a fire escape.

Sam suffered a pelvic injury, torn ligaments, a punctured lung, and a broken leg during the accident.